The Annapurna Circuit is not a trek you do - it is a trek that does something to you. Over 21 days you walk through ecosystems as different as the Amazon and the Arctic, from subtropical rice paddies where buffalo plough fields to the barren moonscape of the Thorong La pass at 5,416 metres.
The teahouses of the circuit are a civilisation unto themselves. Run almost entirely by women whose husbands work in Kathmandu or abroad, they serve dal bhat - lentil soup, rice, vegetables - in quantities that seem impossible until you realise your body is burning 5,000 calories a day. The wifi is slow; the conversation is fast.
Manang, at 3,500 metres, is where trekkers spend an acclimatisation day. A local doctor runs a clinic for altitude sickness - she has seen every permutation of hubris and miscalculation. The town has a bakery that produces apple pie from Himalayan apples; eating it in the cold afternoon sun, looking up at Gangapurna, is one of trekking's great small pleasures.
Thorong La on a clear morning is pure theatre. You move slowly, each step deliberate, the air too thin to hold a full breath. Then the summit cairns appear, strung with prayer flags that flap and crack in the wind. Below, on the other side, Muktinath sits in its desert valley - a place sacred to both Hindus and Buddhists, where 108 stone waterspouts pour holy water year-round.